Zero turn radius mower controls

ABSTRACT

A zero turn radius (ZTR) mower that includes an electric powertrain. The electric powertrain of the ZTR mower includes one or more electric storage batteries, a plurality of electric wheel drive motors that each drives one of the rear wheels of the ZTR mower and a plurality of electric blade motors that each drives one of the plurality of cutting blades mounted to a mower deck. The electric powertrain includes a master controller operable to selectively control the supply of electric power from the electric storage battery to the pair of electric wheel drive motors and the plurality of electric blade motors. The master controller controls the speed and direction of movement of the ZTR mower through user inputs. The master controller is able to separately control the operational speed of each of the electric blade motors based upon the direction and speed of movement of the ZTR mower.

CROSS REFERENCE TO RELATED APPLICATION

The present application is based on and claims priority to U.S.Provisional Patent Application Ser. No. 62/445,390 filed Jan. 12, 2017,the disclosure of which is incorporated herein by reference.

BACKGROUND

The present disclosure relates to a zero turn radius (ZTR) mower. Morespecifically, the present disclosure relates to a ZTR mower thatincludes an electric powertrain including a one or more electric storagebatteries, a plurality of electric wheel drive motors and a plurality ofelectric blade motors.

ZTR mowers have become a popular type of lawn mowing equipment andinclude a pair of independently driven rear wheels. The independentdrive of the rear wheels allows the ZTR mower to be extremelymaneuverable and operable at relative high mowing speeds. ZTR mowers arepopular with landscaping companies and homeowners that have asubstantial amount of acreage to mow on a regular basis.

ZTR mowers typically include an internal combustion engine thattransfers drive power through hydrostatic transaxles to the pair ofdrive wheels. Each of the drive wheels are independently driven atdifferent speeds and even in different directions, which creates theextreme maneuverability of the ZTR mower.

Recently, outdoor power equipment manufacturers, like many otherindustries, have embraced the trend of utilizing electric storagebatteries as an alternate power supply to gas powered engines. In orderto use a battery power supply, the hydrostatic drive motors in ZTRmotors must be removed and replaced by separate electric wheel drivemotors for each of the two rear drive wheels as well as one or moreelectric motors for rotating the plurality of mowing blades. Sincemultiple electric motors must be utilized, a complex control system mustbe employed to accurately control and synchronize the rotational speedof the electric blade motors and the speed and direction of the electricwheel motors. The present disclosure provides a control system forcontrolling the rotational speed of all of the electric motors utilizedin an electric ZTR mower.

SUMMARY

The present disclosure relates to a zero turn radius (ZTR) mower thathas a pair of rear drive wheels and a mowing deck including a pluralityof cutting blades. The ZTR mower includes an electric storage batterythat may include a plurality of battery packs. The battery provides theoperation power to drive at least two electric wheel motors that areeach operable to rotate one of the rear drive wheels. The ZTR mowerfurther includes plurality of electric blade motors that are eachoperable to rotate one of the plurality of cutting blades. A mastercontroller is in communication with each of the two wheel motors and theplurality of blade motors. The master controller is operable to controlthe speed and rotational direction of each of the two wheel motors andthe plurality of blade motors.

In one embodiment, the master controller receives user inputs from apair of control paddles and operates the pair of electric wheel motorsto move the ZTR mower in a desired manner during cutting operation. Themaster controller can receive user inputs from other types of inputdevices and operates the electric wheel motors to control movement ofthe ZTR mower.

In one embodiment, the master controller controls each of the blademotors separately such that the cutting blades can rotate at differentspeeds. The operational speed of each of blade motors can be adjustedbased on the speed of the wheel motors such that the cutting bladesrotate at a desired speed based on the speed of movement of the ZTRmower.

In yet another embodiment, the cutting deck of the ZTR mower canincluded first and second outer cutting blades driven by outer blademotors which are located on opposite sides of the cutting deck. Themaster controller operates the first outer blade motor at a higher speedthan the second outer blade motor when the mower turns in a firstdirection and operates the first outer blade motor at a lower speed thanthe second outer blade motor when the mower turns in a second, oppositedirection. Such operation maintains a desired quality of cut when theZTR mower turns sharply.

In yet another alternate embodiment, the cutting blade rotation can bestopped or greatly reduced by the master controller when the ZTR moweris not moving or when the speed of the electric wheel motors fall belowa minimum threshold. Reducing the operation speed of the blade motorswhen the mower is either stationary or moving at a very slow speedreduces the power draw on the battery and extends the battery chargelife.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings illustrate the best mode presently contemplated of carryingout the disclosure. In the drawings:

FIG. 1 is an isometric view of a ZTR mower incorporating a internalcombustion engine according to some embodiments;

FIG. 2 is a schematic illustration of a ZTR mower utilizing an electricpowertrain including a battery power supply and electric drive motorsaccording to some embodiments;

FIG. 3 is schematic illustration of the control connections between themultiple controllers for each of the electric drive motors and a mastercontroller according to the prior art; and

FIG. 4 is an electric schematic illustration showing the implementationof the present disclosure utilizing a single controller to control theoperation of multiple electric drive motors according to someembodiments.

DETAILED DESCRIPTION

FIG. 1 illustrates an isometric view of a zero turn radius (ZTR) moweras is currently available from numerous manufacturers. The ZTR mower 10includes a main vehicle frame 12, front castor wheels 14, a pair of reardrive wheels 16 and a seat 18. The ZTR mower 10 includes a mower deck 20that includes a cutting assembly positioned between the front castorwheels 14 and the rear drive wheels 16. The mower deck 20 includes frontcastor wheels 22 that aid in maintaining the height of the mower deck 20during cutting operations. In past embodiments, such as shown in FIG. 1,the ZTR mower 10 included an internal combustion engine 24 that providesthe required motive force to drive the rear wheels 16 as well the rotatethe multiple mower blades contained within the mower deck 20. The driveassembly typically includes separate drive assemblies to control therear drive wheels 16 independently. The drive wheels are controlledthrough the position of a pair of control paddles 26. The independentcontrol of the drive wheels 16 allows the ZTR mower to maneuver in a wayto increase the usability of the ZTR mower. Although the pair of controlpaddles 26 are shown in the drawing figures, the control paddles 26could be replaced by a steering wheel, a pair of joysticks, a singlejoystick or any other device or mechanism that would indicate a userdesired direction of movement for the ZTR mower 30.

Although the prior art embodiment shown in FIG. 1 functions wellutilizing the internal combustion engine 24, new designs are beingcreated to replace the internal combustion engine 24 with anall-electric drivetrain that includes one or more lithium ion batterypacks that provide power to multiple electric drive motors.

FIG. 2 is a schematic illustration of the electric drivetraincontemplated in accordance with the present disclosure to create anall-electric ZTR mower 30. As shown in the embodiment of FIG. 2, themower deck 20 encloses three sets of cutting blades 32 (32 a, 32 b and32 c). The cutting blades are oriented such that the cutting blade 32 ais the outer cutting blade on the left side of the mower deck 20 and thecutting blade 32 c is the outer cutting blade on the right side of themower deck 20. In the embodiment shown, a single center cutting blade 32b is positioned between the pair of outer cutting blades 32 a and 32 c.However, additional cutting blades could be included in the mower deckbetween the outer cutting blades.

Each of the cutting blades 32 is driven by an electric cutting blademotor 34 (34 a, 34 b and 34 c). The cutting blade motors 34 are eachdriven by a battery power supply 36 that is connected to the cuttingblade motors 34 though a master controller 52, as will be discussed ingreater detail below. Although the battery 36 is shown in FIG. 2 as asingle component, it is contemplated that the battery power supply 36would include multiple battery packs connected in parallel to provide anoutput voltage. The multiple battery packs are contemplated as beinglithium ion battery packs that included twenty individual cells eachhaving a maximum output of 4.2 V for a maximum output voltage ofapproximately of 84 volts and a nominal voltage of 74 volts for theentire pack. Other configurations and voltages are contemplated for thebattery power supply 36 and the above describes only one currentlycontemplated embodiment.

The electric ZTR mower 30 shown in FIG. 2 further includes a first rearwheel drive motor 38 and a second rear wheel drive motor 40. The firstwheel motor 38 drives a first rear drive wheel 16 while the second wheelmotor 40 drives the rotation of a second rear drive wheel 17. Both ofthe first and second wheel motors 38, 40 are powered by the batterypower supply 36 through the same master controller 52.

As can be understood in FIG. 2, the electric ZTR mower 30 includes fiveseparate and independent electric motors. Three of the electric motors34 are used to rotate the cutting blades 32 while wheel motors 38 and 40are used to independently operate the rear drive wheels 16 and 17. Therotational speed and rotational direction of each of the electric drivemotors 34, 38 and 40 must be controlled through separate control signalssince the motors operate independently from each other.

FIG. 3 illustrates a conventional, prior art control technique that wasutilized to control each of the individual electric motors in currentlyavailable electric ZTR mowers. As shown in FIG. 3, each of the blademotors 34 a, 34 b, 34 c and each of the wheel motors 38 and 40 includesa separate controller 42. The separate controllers 42 independentlycontrol the rotational speed and rotational direction of the individualmotor. Each of the controllers 42 receives power from the battery 36 andsupplies the electrical power from the battery 36 to the individualelectric motor as needed. In the typical arrangement shown in FIG. 3, amaster controller 44 includes multiple control lines 46 that provide theoperational control signals for each of the individual controllers 42.The master controller 44 receives user inputs 45, which can be bladespeed, drive speed, drive direction and other related signals andinterprets these signals. The user input signals can come from thecontrol paddles 26 and other input selectors contained on the ZTR mower.Once the input signals from the user have been interpreted, the mastercontroller 44 sends out control signals along the control lines 46 tothe individual motor controllers 42. The motor controllers, in turn,generate motor control signals that control the rotational speed of thecutting blades and the speed of the drive wheels. As can be understoodin the embodiment shown in FIG. 3, the control system 48 includes fiveseparate motor controllers 42 and a master controller 44. In pastsystems, the individual controllers 42 did not communicate with eachother and only received command signals from the master controller 44.The master controller 44, in turn, did not have the capability ofcontrolling the operation of the motors 34, 38 and 40 in a coordinatedmanner as may be desired.

FIG. 4 illustrates a schematic implementation of a control system 50contemplated in accordance with the present disclosure. In theembodiment of FIG. 4, the three cutting blade motors 34 a, 34 b and 34c, as well as the pair of wheel motors 38 and 40 are each controlled bythe same, single master controller 52 through a series of control lines54. The master controller 52 is able to independently controller thespeed and direction of rotation of each of the wheel motors 38 and 40and the speed of rotation of the cutting blade motors 34. The mastercontroller 52 receives user inputs 56 from various differing componentsof the electric ZTR mower. These user inputs may be related to theposition of the control paddles 26, desired rotational speeds for themower blades selected by the user from a control panel on the mower orany other input that may be related to the operation speed or directionof either the three blade motors 34 or the wheel motors 38, 40.

Since the position of the control paddles 26 is needed to controlsteering and speed through the relative drive speeds of the wheel motors38 and 40, position sensors must be utilized to provide an electricsignal to the master controller as to the position of the controlpaddles 26. These position sensors can be located in any position inwhich the position sensors can detect the movement and position of thecontrol paddles 26. The position sensors would communicate directly tothe master controller 52 and would thus allow “drive by wire”capabilities for the electric ZTR mower. The control paddles could bereplaced with other types of controls, such as a pair of joysticks.However, it is believed that the function and overall acceptance of theZTR mower is due in part to the pair of control paddles 26 and suchconfiguration is contemplated in the present disclosure. No matter thecontrol device used by the user, signals are directed to the mastercontroller 52 to indicate both the speed and direction of rotation ofthe rear wheels. These signals are received and interpreted by thesingle master controller 52.

As can be understood in FIG. 4, utilizing a single controller 52 tocontrol the operation of the five electric drive motors allows the motorcontroller 52 to more precisely coordinate the operation of the electricmotors to enhance the operability of the electric ZTR mower 30. Suchcoordination was not feasible in the configuration shown in FIG. 3,which utilized the master controller 44 and the five separate motorcontrollers 42. Such coordination allows the master controller 52 tocarry out various enhancements to the normal operation of a ZTR mower,as will be described below.

In a first illustrative example of the enhanced operation of the ZTRmower, the controller 52 could coordinate the rotational speed of theblade motors 34 based upon the operational speed of the wheel motors 38,40. For example, when the wheel motors 38, 40 are operating at a higherrate of speed, the master controller 52 would increase the rotationalspeed of the blade motors 34 to enhance the quality of cut when the ZTRmower 30 is moving more quickly along the ground. The master controller52 would slow the rotational speed of the blade motors 34 when the speedof rotation of the wheel motors slow, since the ZTR mower would bemoving more slowly along the ground. Decreasing the operating speed ofthe blade motors 34 based on the speed of mowing would reduce the powerdraw of the blade motors 34 while still maintaining a desired quality ofcut.

In another illustrative example of the operation of the ZTR mower, themaster controller 52 could turn off the blade motors 34 when the wheelmotors 38, 40 are operating at a very low speed, indicating that the ZTRmower is either idling or stopped. The master controller 52 would set aminimum speed threshold for the wheel motors 38, 40 and if the speed ofthese motors falls below the minimum threshold, the blade motors 34could either be turned off entirely or allowed to rotate at a greatlyreduced speed. By terminating operation of the blade motors 34 when themower is not moving, the master controller 52 would enhance the batterylife 36 by operating the blade motors 34 only as fast or when needed.

In another illustrative example, the master controller 52 could send“pulsed” voltages to the blade motors 34 to reduce the power consumptionof each of the blade motors 34 rather than simply supplying a constantvoltage to the blade motors 34. In such operation, the voltage from thebattery supply would be pulsed successively between the blade motors 34and the system would rely upon the rotational inertia of the cuttingblades to keep the blades rotating during the periods of time when theblade is not under active drive by the blade motor 34. Thisconfiguration would reduce the voltage draw since voltage would not beapplied to the blade motor 34 continuously.

In yet another illustrative example, the controller 52 can receivetorque feedback from each of the three blade motors 34 and can determinewhich of the three blade motors 34 is under the heaviest load. Suchunbalanced loading may result during sharp turning of the ZTR mowersince during such sharp turns, the outer cutting blade is traveling overthe grass being cut at a much higher rate of speed as compared to theinner cutting blade. As an example, if the user indicates a desire,through the position of the control paddles 36, to turn sharply to theleft as viewed in FIG. 2, the speed of the motor 38 is slowed orreversed and the speed of the motor 40 is increased. During this sharpleft turn, the outer cutting blade 32 a would be covering much lessground than the outer cutting blade 32 c. Therefore, it would bedesirable to increase the rotational speed of the outer cutting blade 32c relative to the outer cutting blade 32 a. Since the master controller52 would receive all of the inputs from the blade motors 34, the mastercontroller could quickly and responsively control the rotating speed ofthe cutting blades 32 a and 32 c through the blade respective blademotors 34.

The master controller 52 will also know the turning angle of the ZTRmower since the master controller 52 would receive signals related tothe position of the control paddles 26, which are used to control theoperational speed of the wheel motors 38, 40. Based on the turningangle, the controller 52 would increase the speed of the blade motor onthe side with the faster moving drive wheel while the opposite side maycall for a reduction in blade speed since it might be moving very slowlyor even standing in place. The measured blade motor torque could alsoidentify an unbalanced load on the mower blades, which may call forspeeding up one of the blade motors and possibly slowing down the otherblade motor. Further, the controller could slow down the wheel motors38, 40 to allow the blade motors to keep up with the cutting load.

As can be understood in the embodiment of FIG. 4, the battery 36provides power for both the controller and each of the individual drivemotors. The connection between the battery 36 and the drive motors 34,38 and 40 could be varied depending upon the specific implementation ofthe present disclosure.

This written description uses examples to disclose the invention,including the best mode, and also to enable any person skilled in theart to make and use the invention. The patentable scope of the inventionis defined by the claims, and may include other examples that occur tothose skilled in the art. Such other examples are intended to be withinthe scope of the claims if they have structural elements that do notdiffer from the literal language of the claims, or if they includeequivalent structural elements with insubstantial differences from theliteral languages of the claims.

The invention claimed is:
 1. A zero turn radius (ZTR) mower having apair of rear drive wheels and a mowing deck including a plurality ofcutting blades, comprising: an electric storage battery; a pair ofelectric wheel motors each operable to rotate one of the rear drivewheels; a plurality of electric blade motors each operable to rotate oneof the plurality of cutting blades; and a master controller incommunication with each of the pair of wheel motors and the plurality ofblade motors, wherein the master controller is operable to control thespeed and rotational direction of each of the pair of wheel motors andthe plurality of blade motors and wherein the master controller isoperable to stop rotation of the cutting blades when the wheel motorsare operating below a threshold speed.
 2. The ZTR mower of claim 1wherein the master controller is operable to receive user inputs and tocontrol the rotational direction and speed of the pair of wheel motorsbased on the user inputs.
 3. The ZTR mower of claim 1 wherein the mastercontroller is operable to adjust the rotational speed of the blademotors based on the speed and direction of the wheel motors.
 4. The ZTRmower of claim 1 wherein the master controller is operable to adjust therotational speed of the plurality of blade motors separately such thatthe cutting blades selectively rotate at different speeds.
 5. The ZTRmower of claim 4 wherein the plurality of blade motors include a firstouter blade motor and a second outer blade motor positioned on oppositesides of the mowing deck, wherein the master controller operates thefirst outer blade motor at a higher speed than the second outer blademotor when the mower turns in a first direction and operates the firstouter blade motor at a lower speed than the second outer blade motorwhen the mower turns in a second direction.
 6. An electric powertrainfor use with a zero turn radius (ZTR) mower having a pair of rear drivewheels and a mowing deck including a plurality of cutting blades,comprising: an electric storage battery; a pair of electric wheel motorseach operable to rotate one of the rear drive wheels; a plurality ofelectric blade motors each operable to rotate one of the plurality ofcutting blades; and a master controller in communication with each ofthe pair of wheel motors and the plurality of blade motors, wherein themaster controller is operable to control the speed and rotationaldirection of each of the pair of wheel motors and the plurality of blademotors and wherein the master controller is operable to stop rotation ofthe cutting blades when the wheel motors are operating below a thresholdspeed.
 7. The electric powertrain of claim 6 wherein the mastercontroller is operable to receive user inputs and to control therotational direction and speed of the pair of wheel motors based on theuser inputs.
 8. The electric powertrain of claim 6 wherein the mastercontroller is operable to adjust the rotational speed of the blademotors based on the speed of the wheel motors.
 9. The electricpowertrain of claim 6 wherein the master controller is operable toadjust the rotational speed of the plurality of blade motors separatelysuch that the cutting blades selectively rotate at different speeds. 10.The electric powertrain of claim 9 wherein the plurality of blade motorsinclude a first outer blade motor and a second outer blade motorpositioned on opposite sides of the mowing deck, wherein the mastercontroller operates the first outer blade motor at a higher speed thanthe second outer blade motor when the mower turns in a first directionand operates the first outer blade motor at a lower speed than thesecond outer blade motor when the mower turns in a second direction. 11.A method of operating a zero turn radius (ZTR) mower having a pair ofrear drive wheels and a mowing deck including a plurality of cuttingblades, comprising the steps of: mounting a plurality of electric blademotors on the mower deck in a position such that each of the electricblade motors rotates one of the cutting blades; mounting a pair ofelectric wheel motors in a position such that each electric wheel motorrotates one of the rear drive wheels; providing an electric storagebattery on the mower; connecting a single master controller to thebattery and the plurality of electric blade motors and the pair ofelectric wheel motors; operating the master controller to supplyelectric power from the battery to control the speed and rotationaldirection of each of the pair of electric wheel motors and the pluralityof electric blade motors and stop rotation of the electric blade motorswhen the electric wheel motors are rotating below a threshold speed. 12.The method of claim 11 wherein the master controller adjusts therotational speed of the plurality of electric blade motors based on therotation speed of the pair of electric wheel motors.
 13. The method ofclaim 12 wherein the rotational speed of the plurality of electric blademotors is adjusted independently from each other.
 14. The method ofclaim 13 wherein the plurality of blade motors includes a first outerblade motor and a second outer blade motor positioned on opposite sidesof the mowing deck, wherein the master controller operates the firstouter blade motor at a higher speed than the second outer blade motorwhen the motor turns in a first direction and the master controlleroperates the first outer blade motor at a lower speed than the secondouter blade motor when the mower turns in a second direction.
 15. Themethod of claim 11 wherein the electric power is supplied to theelectric wheel motors and the electric blade mowers in a series ofpulses to control the rotational speed of the motors.
 16. The method ofclaim 11 further comprising the step of adjusting the rotational speedof the electric blade motors as the mower turns.